Systems for low power distribution in a power distribution network

ABSTRACT

Systems for low power distribution in a power distribution network (PDN) contemplate using multiple low-power conductors to convey power from a power source to a remote sub-unit. The multiple conductors are isolated from one another to help prevent overcurrent conditions in a fault condition. In a first exemplary aspect, the isolation is provided by galvanic isolation. In a second exemplary aspect, the isolation is provided by diodes at the remote sub-units. Further, current sensors may be used at the power source to detect if any of the multiple low-power conductors are carrying current above a defined threshold current. By providing one or more of these safety features, a multiplexer may not be needed at the remote sub-unit, thus providing cost savings while preserving the desired safety features.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. § 119 ofU.S. Provisional Application Ser. No. 63/058,138, filed Jul. 29, 2020,the content of which is relied upon and incorporated herein by referencein its entirety.

BACKGROUND

The technology of the disclosure relates to a power distribution network(PDN) and more particularly, to a low-power PDN.

Electrical devices require power. In many instances, the power may beprovided by a battery or a local power source such as a wall outlet orthe like. However, in some instances, it may be inconvenient to supplypower through a wall outlet or a battery. For example, the power demandsor voltage levels of the device being powered may exceed that which isavailable through the conventional wall outlets (e.g., the item may need340 Volts (V) instead of the conventional 110 V supplied by most USpower outlets). Or, the device may consume sufficient power that batterysupplies are impractical. Likewise, the location may be such that alocal power supply is not available. In such instances, there may be adedicated PDN associated with such devices.

A few exemplary systems that may have associated PDNs include, but arenot limited to, server farms, lighting systems, and distributedcommunication systems (DCSs) such as a distributed antenna system (DAS)or radio access network (RAN). Such systems may have a central powersource and one or more power conductors that convey power from the powersource to one or more remote sub-units (e.g., a server, a lightingfixture, a remote antenna unit, or the like). There is a concern that ahuman may come into contact with the power conductors and be shocked orelectrocuted by such contact. Accordingly, some regulations, such asInternational Electric Code (IEC) 60950-21, may limit the amount ofdirect current (DC) that is remotely delivered by the power source overthe conductors to less than the amount needed to power the remotesub-unit during peak power consumption periods for safety reasons.

One solution to remote power distribution limitations is to employmultiple conductors and split current from the power source over themultiple conductors, such that the power on any one electrical conductoris below the regulated limit. However, such multi-conductor arrangementsmay need complicated and expensive multiplexers at the remote sub-units.

No admission is made that any reference cited herein constitutes priorart. Applicant expressly reserves the right to challenge the accuracyand pertinency of any cited documents.

SUMMARY

Embodiments disclosed herein include systems for low power distributionin a power distribution network (PDN). In exemplary aspects, multiplelow-power conductors are employed to convey power from a power source toa remote sub-unit. The multiple conductors are isolated from one anotherto help prevent overcurrent conditions in a fault condition. In a firstexemplary aspect, the isolation is provided by galvanic isolation. In asecond exemplary aspect, the isolation is provided by diodes at theremote sub-units. Further, current sensors may be used at the powersource to detect if any of the multiple low-power conductors arecarrying current above a defined threshold current. By providing one ormore of these safety features, a multiplexer may not be needed at theremote sub-unit to prevent overcurrent situations, thus providing costsavings while preserving the desired safety features.

In this regard, in one embodiment, a remote sub-unit is disclosed. Theremote sub-unit comprises a power input port configured to be coupled totwo power conductors. The remote sub-unit also comprises a first diodecoupled to the power input port and a first one of the two powerconductors. The remote sub-unit also comprises a second diode coupled tothe power input port and a second one of the two power conductors.

In another embodiment, a power source is disclosed. The power sourcecomprises a power input configured to receive power. The power sourcealso comprises a plurality of power outputs configured to operate at alow power level. Each of the plurality of power outputs is galvanicallyisolated from others of the plurality of power outputs by a respectivetransformer.

In another embodiment, a power source is disclosed. The power sourcecomprises a power input configured to receive power. The power sourcealso comprises a power output port configured to couple to a two-wirepower conductor pair. The power source also comprises a first conductorcoupling the power input to the power output port. The power source alsocomprises a first current sensor associated with the first conductor andconfigured to measure current on the first conductor. The power sourcealso comprises a first switch associated with the first conductor. Thepower source also comprises a control circuit. The control circuit isconfigured to receive information from the first current sensor. Thecontrol circuit is also configured to open the first switch responsiveto the information indicating an overcurrent situation on the firstconductor.

In another embodiment, a PDN is disclosed. The PDN comprises a powersource. The power source comprises a power input configured to receivepower. The power source also comprises a power output port. The powersource also comprises a first conductor coupling the power input to thepower output port. The power source also comprises a first currentsensor associated with the first conductor and configured to measurecurrent on the first conductor. The power source also comprises a firstswitch associated with the first conductor. The power source alsocomprises a control circuit. The control circuit is configured toreceive information from the first current sensor. The control circuitis also configured to open the first switch responsive to theinformation indicating an overcurrent situation on the first conductor.The PDN also comprises a power conductor pair coupled to the poweroutput port. The PDN also comprises a remote sub-unit. The remotesub-unit comprises a remote sub-unit power input port coupled to thepower conductor pair. The remote sub-unit also comprises a first diodecoupled to the remote sub-unit power input port and a first one of thepower conductor pair. The remote sub-unit also comprises a second diodecoupled to the remote sub-unit power input port and a second one of thepower conductor pair.

In another embodiment, a distributed communication system (DCS) isdisclosed. The DCS comprises a PDN. The PDN comprises a power source.The power source comprises a power input configured to receive power.The power source also comprises a power output port. The power sourcealso comprises a first conductor coupling the power input to the poweroutput port. The power source also comprises a first current sensorassociated with the first conductor and configured to measure current onthe first conductor. The power source also comprises a first switchassociated with the first conductor. The power source also comprises acontrol circuit. The control circuit is configured to receiveinformation from the first current sensor. The control circuit is alsoconfigured to open the first switch responsive to the informationindicating an overcurrent situation on the first conductor. The PDN alsocomprises a power conductor pair coupled to the power output port. ThePDN also comprises a plurality of remote sub-units. Each remote sub-unitcomprises a remote sub-unit power input port coupled to the powerconductor pair. Each remote sub-unit also comprises a first diodecoupled to the remote sub-unit power input port and a first one of thepower conductor pair. Each remote sub-unit also comprises a second diodecoupled to the remote sub-unit power input port and a second one of thepower conductor pair. The DCS also comprises a central unit. The centralunit is configured to distribute received one or more downlinkcommunications signals over one or more downlink communications links toone or more remote sub-units. The central unit is also configured todistribute received one or more uplink communications signals from theone or more remote sub-units from one or more uplink communicationslinks to one or more source communications outputs. Each remote sub-unitamong the plurality of remote sub-units is configured to distribute thereceived one or more downlink communications signals received from theone or more downlink communications links to one or more client devices.Each remote sub-unit is also configured to distribute the received oneor more uplink communications signals from the one or more clientdevices to the one or more uplink communications links.

Additional features and advantages will be set forth in the detaileddescription which follows and, in part, will be readily apparent tothose skilled in the art from the description or recognized bypracticing the embodiments as described in the written description andclaims hereof, as well as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description are merely exemplary and are intendedto provide an overview or framework to understand the nature andcharacter of the claims.

The accompanying drawings are included to provide a furtherunderstanding of the disclosure, and are incorporated in and constitutea part of this specification. The drawings illustrate one or moreembodiment(s), and together with the description serve to explainprinciples and operation of the various embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an exemplary power distribution network(PDN) for a distributed communication system (DCS), where the PDN mayhave start-up protocols according to exemplary aspects of the presentdisclosure;

FIG. 2 is a schematic diagram of an exemplary PDN for a server farm,where the PDN may have start-up protocols according to exemplary aspectsof the present disclosure;

FIG. 3 is a schematic diagram of an exemplary PDN for a lighting system,where the PDN may have start-up protocols according to exemplary aspectsof the present disclosure;

FIG. 4A is a block diagram showing a conventional PDN where a remotesub-unit receives power from a power source through multiple conductors;

FIG. 4B is a block diagram of the PDN of FIG. 4A having a first type offault in the conductors connecting the power source to the remotesub-unit;

FIG. 4C is a block diagram of the PDN of FIG. 4A having a second type offault in the conductors connecting the power source to the remotesub-unit;

FIG. 5 is a block diagram of a PDN where the power source hasgalvanically-isolated output ports to prevent overcurrent conditions;

FIG. 6 is a block diagram of a remote sub-unit in a PDN, where theremote sub-unit is powered through a low-power conductor and hasisolation between conductors provided by diodes;

FIG. 7 is a block diagram of a power source with sensors includingcurrent and voltage sensors to assist in detection and correction ofovercurrent situations;

FIG. 8 is a block diagram of a power source similar to the power sourceof FIG. 7 , but with redundant control circuits and switches to assistin detection and correction of overcurrent situations;

FIG. 9 is a block diagram of a PDN that may include the remote sub-unitof FIG. 6 and/or the power source of FIG. 7 or 8 ;

FIG. 10 is a schematic diagram of an exemplary optical fiber-based DCSconfigured to distribute communications signals between a central unitand a plurality of remote sub-units, and that can include one or morePDNs, including the PDNs in FIG. 5 or 9 ;

FIG. 11 is a partially schematic cut-away diagram of an exemplarybuilding infrastructure in which the DCS in FIG. 10 can be provided;

FIG. 12 is a schematic diagram of an exemplary mobile telecommunicationsenvironment that includes an exemplary radio access network (RAN) thatincludes a mobile network operator (MNO) macrocell employing a radionode, a shared spectrum cell employing a radio node, an exemplary smallcell RAN employing a multi-operator radio node located within anenterprise environment as DCSs, and that can include one or more PDNs,including the PDNs in FIG. 5 or 9 ;

FIG. 13 is a schematic diagram an exemplary DCS that supports 4G and 5Gcommunications services, and that can include one or more PDNs,including the PDNs in FIG. 5 or 9 ; and

FIG. 14 is a schematic diagram of a generalized representation of anexemplary controller that can be included in any component or circuit ina power distribution system, including the PDNs in FIG. 5 or 9 , whereinan exemplary computer system is adapted to execute instructions from anexemplary computer-readable link.

DETAILED DESCRIPTION

Reference will now be made in detail to the embodiments, examples ofwhich are illustrated in the accompanying drawings, in which some, butnot all embodiments are shown. Indeed, the concepts may be embodied inmany different forms and should not be construed as limiting herein;rather, these embodiments are provided so that this disclosure willsatisfy applicable legal requirements. Whenever possible, like referencenumbers will be used to refer to like components or parts.

Embodiments disclosed herein include systems for low power distributionin a power distribution network (PDN). In particular, exemplary aspectsof the present disclosure contemplate using multiple low-powerconductors to convey power from a power source to a remote sub-unit. Themultiple conductors are isolated from one another to help preventovercurrent conditions in a fault condition. In a first exemplaryaspect, the isolation is provided by galvanic isolation. In a secondexemplary aspect, the isolation is provided by diodes at the remotesub-units. Further, current sensors may be used at the power source todetect if any of the multiple low-power conductors are carrying currentabove a defined threshold current. By providing one or more of thesesafety features, a multiplexer may not be needed at the remote sub-unitto prevent overcurrent situations, thus providing cost savings whilepreserving the desired safety features.

A PDN rarely exists in isolation. Rather, a PDN provides infrastructureto some other system, a few of which are briefly discussed withreference to FIGS. 1-3 . Some PDNs may provide power at voltage levelsabove 60 Volts (V) and over 100 Watts (W). However, other PDNs may fallbelow these thresholds and be categorized as low-power networks.Problems that may arise in PDNs such as those illustrated in FIGS. 1-3are discussed with reference to FIGS. 4A-4C. Solutions according to thepresent disclosure are discussed below beginning with reference to FIG.5 .

In this regard, FIG. 1 illustrates a simplified block diagram of adistributed communication system (DCS) 100. The DCS 100 may include ahead end unit (HEU) 102 that communicates through a communication medium104 with a remote antenna unit (RAU) 106. The communication medium 104may be a wire-based or optical fiber medium. The RAU 106 includes atransceiver and an antenna (not illustrated) that communicate wirelesslywith mobile terminals and other user equipment (also not illustrated).Because the RAU 106 sends and receives wireless signals and maypotentially perform other functions, the RAU 106 consumes power. Thatpower may, in some instances, be provided locally. More commonly, and ofinterest to the present disclosure, the DCS 100 includes a PDN, and theRAU 106 receives power from a power source 108 that transmits power tothe RAU 106 over power lines 110 formed from a positive power line 110+and a negative power line 110−. The power lines 110 may be many meterslong, for example, extending through an office building, across multiplefloors of a multi-story building, or the like. Further, the power lines110 may couple to multiple RAUs 106 (even though only one is illustratedin FIG. 1 ). The power source 108 may be coupled to an external powergrid 112.

Similarly, FIG. 2 illustrates a data center system 200 having a powersource 108 coupled to remote data servers 202 through power lines 204.The power source 108 is coupled to the external power grid 112. As withthe RAU 106, the data servers 202 may consume power supplied through thepower lines 204.

Similarly, FIG. 3 illustrates a lighting system 300 having a powersource 108 coupled to remote lighting units 302 through power lines 304.The power source 108 is coupled to the external power grid 112. As withthe RAU 106, the remote lighting units 302 may consume power suppliedthrough the power lines 304.

It should be appreciated that there may be other contexts that may use aPDN, and the examples provided in FIGS. 1-3 are not intended to belimiting. As a note of nomenclature, the RAU 106, the remote dataservers 202, and the lighting units 302 are remote sub-units.

The power requirements of the remote sub-units typically control howmuch power is provided to the remote sub-units through an associatedPDN. Many governments provide regulations or statutes relating to howpower may be provided to the remote sub-units through a PDN. Most suchregulations or statutes come from standard settings bodies likeUnderwriters Laboratories (UL) or the National Fire ProtectionAssociation's National Electric Code (NEC). In many cases the ULstandard and the NEC overlap such that compliance with one also meanscompliance with the other.

While there may be other ways to differentiate power provision, thepresent disclosure contemplates a high-power format and a low-powerformat based on the UL60950-1 provided by Underwriters Laboratories andNEC Class-2. Compliance with these two standards is considered herein alow-power format while providing power above the thresholds set by thesetwo standards is considered herein a high-power format. These twostandards require less than 60 V and less than 100 W. Additionally, thewire gauge used to comply with these standards is between thirty andtwelve American wire gauge (30-12 AWG). Staying below these thresholdshas the benefit of eliminating a requirement for a separate wiringconduit and does not require a licensed electrician to install.

As noted above, the requirements of the remote sub-unit may dictate howmuch power is supplied by the PDN. When the remote sub-unit requiresmore than 100 W of power, there are generally two ways such powerrequirements are satisfied. The first way is through a high-powerformat. Corning Optical Communications, assignee of the presentdisclosure, has several solutions that meet the requirements for ahigh-power format, and these approaches are not directly of interest tothe present disclosure. The second way is to provide multiple powerconnections to the remote sub-unit from the power source, where eachsuch connection complies with the low-power format.

While the concept of using multiple low-power format connections in aPDN seems simple, there may be situations where current from oneconnection may “spill over” or “spill onto” another connection. Suchconditions may result in the low-power format thresholds being exceeded.A conventional PDN 400 is illustrated in FIG. 4A and two such faultconditions are illustrated herein with reference to FIGS. 4B and 4C.

In this regard, FIG. 4A illustrates the PDN 400. Specifically, the PDN400 includes a power source 402, which may be a limited power system(LPS) that complies with NEC Class-2. The PDN 400 further includes aremote sub-unit 404 (e.g., a remote antenna unit or the like). The powersource 402 may include a first output port 406(1) that couples toconductors 408P(1), 408N(1), a second output port 406(2) that couples toconductors 408P(2), 408N(2), up through an mth output port 406(M) thatcouples to conductors 408P(M), 408N(M). Within the remote sub-unit 404,the conductors 408P(1)-408P(M) are connected at an input port 410, andthe conductors 408N(1)-408(M) are connected at the input port 410.Current on a given conductor 408P flows from the respective output port406 to the input port 410 and provides power to a load 412 within theremote sub-unit 404. Current returns from the input port 410 onrespective conductors 408N to the respective output ports 406 asgenerally shown by dotted lines 414(1)-414(M).

A first fault condition is illustrated in FIG. 4B, where, for the sakeof example, the PDN 400 has had a short 416 from across the conductors408P(M) and 408N(M). Current 418(1) on the conductor 408P(1) will arriveat the remote sub-unit 404 and pass to the conductor 408P(M), across theshort 416, back through the conductor 408N(M), and then back through theconductor 408N(1). Similarly, current 418(2) on the conductor 408P(2)will arrive at the remote sub-unit 404 and pass to the conductor408P(M), across the short 416, back through the conductor 408N(M), andthen back through the conductor 408N(2). Current 418(M) leaving theoutput port 406(M) will cross the short 416 and return to the outputport 406(M). The net result of the short 416 is that at least oneconductor pair (e.g., 408P(M), 408N(M)) will have more than the normalcurrent for at least a portion of its length and may exceed the ratingfor the conductor. This situation is undesirable.

FIG. 4C illustrates the PDN 400 with an open circuit instead of a shortcircuit. Such an open circuit is likewise undesirable as the opencircuit may also cause current flow on a conductor to exceed theconductor rating. For the sake of example, the conductor 408N(1) has anopen circuit 420. Current is not able to flow back on the conductor408N(1). Therefore, some portion of current 422(1) will flow back on theconductors 408N(2)-408N(M). This additional current on these conductors408N(2)-408N(M) may cause the current to exceed the rating for theconductor. Again, this situation is undesirable.

Conventional systems are aware of the fault conditions illustrated inFIGS. 4B and 4C. To address these fault conditions, conventional systemsrely on a relatively expensive multiplexer in the remote sub-unit tocombine the power from the various connections while precluding currentfrom passing from one conductor to another in such a manner that wouldcause the connection to exceed the low-power format thresholds. Becausethere may be many remote sub-units in a given PDN, each such expensivemultiplexer has a burden multiplied by the number of remote sub-units.This additional burden leaves room for a more cost effective solution.

Exemplary aspects of the present disclosure provide two solutions thatprevent overcurrent situations that might exceed the low-power standardsin the event of a short circuit or an open circuit. The first solutionis to isolate galvanically output ports at the power source using atransformer for each output port. The second, more elegant solution isto add diodes to the remote sub-unit to prevent current backflow andmonitor current levels on the conductors. When current levels on theconductors exceed a predefined threshold, switches are opened so thatcurrent does not flow on the conductors.

FIG. 5 provides a block diagram of a PDN 500 having a power source 502coupled to a remote sub-unit 504. In particular, the power source 502includes output ports 506(1)-506(R) where each of the output ports506(1)-506(R) are galvanically isolated from one another. Galvanicisolation is a principle of isolating functional sections of electricalsystems to prevent current flow; no direct conduction path is permitted.Energy or information can still be exchanged between the sections byother means, such as capacitance, induction, or electromagnetic waves,or by optical, acoustic, or mechanical means.

Galvanic isolation is used where two or more electric circuits mustcommunicate, but their grounds may be at different potentials. It is aneffective method of breaking ground loops by preventing unwanted currentfrom flowing between two units sharing a ground conductor. The mostcommon form of galvanic isolation is through a transformer, and the PDN500 may use transformers 508(1)-508(R) to isolate the output ports506(1)-506(R) from one another. In particular, the transformers508(1)-508(R) may be positioned between the output ports 506(1)-506(R)and a high voltage-to-low voltage power supply/converter 510. The powersupply/converter 510 may receive power from a high-voltage source suchas a battery or an alternating current (AC) power source such as ahigh-voltage line connected to a public power grid (not shown). Otherforms of galvanic isolation (not illustrated) include opto-isolators,capacitors, Hall effect sensors, magnetocouplers, and isolation relays.

With continued reference to FIG. 5 , the remote sub-unit 504 may includea load 512 and power inputs 514(1)-514(R′), where R′ may be equal to,greater than, or less than R depending on the requirements of the load512 and the cumulative power available from the R output ports 506. Theoutput ports 506(1)-506(R) are coupled to the power inputs514(1)-514(R′) by conductor pairs 516(1)-516(R). The power on theconductor pairs 516(1)-516(R) is summed inside the remote sub-unit 504to provide sufficient power to the load 512.

While galvanic isolation is effective, the use of transformers 508 maybe expensive and/or require relatively large amounts of space (i.e.,transformers at these power levels are not small components).Accordingly, exemplary aspects of the present disclosure provide analternate technique to address overcurrent situations that may occur asa function of a fault in the conductors or other source. In particular,exemplary aspects of the present disclosure contemplate adding diodes tothe conductors in the remote sub-units to prevent undesired currentflow. Additionally, exemplary aspects of the present disclosure addcurrent sensors to the conductors at the power source. When the currentsensors determine that an overcurrent situation is occurring, a controlcircuit may open a switch to interrupt current flow to prevent theovercurrent situation from continuing.

FIG. 6 illustrates a remote sub-unit 600, analogous to the remotesub-unit 504 of FIG. 5 , but including diodes 602P(1)-602P(R′) for thepositive conductors 604P(1)-604P(R′) and diodes 602N(1)-602N(R′) for thenegative conductors 604N(1)-604(R′). Note that the diodes602P(1)-602P(R′) are optional. A load 606 receives the combined powerfrom power inputs 608(1)-608(R′) (analogous to the power inputs514(1)-514(R′) of FIG. 5 ).

By placing the diodes 602N(1)-602N(R′) on the negative conductors604N(1)-604N(R′), current cannot flow back into the remote sub-unit 600.Stopping such current flow effectively addresses the short circuit faultillustrated in FIG. 4B and prevents an overcurrent situation from such ashort circuit. It should be appreciated that diodes capable of handlingthe current flows at the levels associated with low-power operationcompliant with NEC-Class 2 are relatively inexpensive and consumerelatively little space. The cost and size of such diodes helps keep thecost of the remote sub-unit 600 manageable particularly in installationswhere many remote sub-units are installed.

Further aspects of the present disclosure address the open circuit faultcondition illustrated in FIG. 4C. Specifically, current sensors andswitches are added to the power source. FIG. 7 illustrates a first powersource 700 and FIG. 8 illustrates a second power source 800, similar tothe first power source 700, but with redundant features for improvedsafety.

Turning specifically to FIG. 7 , the first power source 700 has currentsensors 702P and 702N which report current levels to a control circuit704. The control circuit 704 controls switches 706P and 706N. Thecurrent sensors 702P, 702N and switches 706P, 706N are associated with(e.g., by being serially positioned within) conductors 708P, 708N withinthe power source 700 that collectively form a low-power (e.g., less than60 V) bus 708. A voltage sensor 710 may also be coupled across theconductors 708P, 708N and report voltage levels to the control circuit704. Collectively the sensors 702P, 702N, 710, switches 706P, 706N, andcontrol circuit 704 may be referred to as an overcurrent safety system711. The conductors 708P, 708N are coupled to an output port 712, whichmay have an individual positive output port 712P and negative outputport 712N. The output port 712 is coupled to conductors 714P, 714N toform a first class-2 power line 716.

With continued reference to FIG. 7 , the power source 700 may furtherinclude a receiver module 718 that receives a high-voltage (e.g., 350 V)direct current (DC) signal 720. This high-voltage DC signal 720 may gothrough a multiplexer or combiner 722 and interoperate with a safetycircuit 724 and/or a controller 726. Alternatively, or in addition, thepower source 700 may receive an AC power signal 728 such as from anexternal power grid (not shown). In an exemplary aspect, the AC powersignal 728 is the primary source of power for the power source 700 whilethe high-voltage DC signal 720 may be from a battery backup. The powersource 700 uses a high voltage-to-low voltage converter 730 to lower theincoming high-voltage signal to a low-power signal (e.g., less than 60V) to be put on the bus 708. The controller 726 may further communicatewith the high voltage-to-low voltage converter 730 (e.g., to pass analarm of power failure or for other reasons as needed or desired).

The power source 700 may have additional output ports 732(1)-732(W),which may be functionally identical to the output port 712. Each of theadditional output ports 732(1)-732(W) may also have associatedovercurrent safety system 734(1)-734(W) (only 734(W) shown) identical tothe overcurrent safety system 711. As an alternative, the controlcircuit 704 may be shared across all the overcurrent safety systems.Optionally, each output port 712 and 732(1)-732(W) may include arespective multiplexer (not shown) and/or a hot swap circuit. Theseoptional elements may be positioned between the respective overcurrentprotection systems and the output ports. Note that the bus 708 may be acommon bus serving all the output ports 712, 732(1)-732(W) or eachoutput port may have a respective isolated low-voltage line.

The power source 700 may further include a general management circuit736 which may manage individual power levels on the bus 708, monitor thecontrol circuits 704, and/or provide management information to thecontroller 726, which in turn may act as a management bridge for thehigh voltage-to-low voltage converter 730. In an exemplary aspect, alink 738 between the general management circuit 736 and the controller726 is a serial peripheral interface (SPI) or other serial link.

FIG. 8 illustrates a power source 800 that is substantially similar tothe power source 700, but has some redundant features to improve safety.Specifically, the overcurrent safety system 711 is replaced by anovercurrent safety system 802(1)-802(W+1) (one for each output port 712,732(1)-732(W)). Each overcurrent safety system 802 includes the currentsensors 702P, 704N and voltage sensor 710. However, the overcurrentsafety system 802 includes an expanded control circuit 804, which mayhave a primary control circuit 806 and a secondary control circuit 808.The primary control circuit 806 controls first switches 810P, 810N,while the secondary control circuit 808 controls second switches 812P,812N. By having two switches for each conductor 708P, 708N and twocontrol circuits, there is an increased likelihood that the conductor708P, 708N will be disconnected to stop an overcurrent situation even ifone switch or control circuit fails.

FIG. 9 shows a PDN 900 where a power source 902, which may be the firstpower source 700 of FIG. 7 or the second power source 800 of FIG. 8 , iscoupled to a remote sub-unit 904, which may be the remote sub-unit 600of FIG. 6 , by conductor pairs 906(1)-906(M). The PDN 900 may be adaptedfor use in any other system such as a lighting system, server farm, DCS,or the like (as generically shown in FIGS. 1-3 ).

In the interests of completeness, one exemplary DCS having a powerdistribution network is explored below with reference to FIGS. 10-13 andan exemplary computer that may be used at various locations within a PDNis illustrated in FIG. 14 . It should be appreciated that the precisecontext for the PDN is not central to the present disclosure.

FIG. 10 is a schematic diagram of an exemplary optical fiber-baseddistributed antenna system (DAS) 1000 in which a PDN can be provided. Inthis example, the PDN 500 of FIG. 5 or the PDN 900 of FIG. 9 is providedin a DCS which is the DAS 1000 in this example. Note that the PDNs 500or 900 are not limited to being provided in a DCS. A DAS is a systemthat is configured to distribute communications signals, includingwireless communications signals, from a central unit to a plurality ofremote sub-units over physical communications media, to then bedistributed from the remote sub-units wirelessly to client devices inwireless communication range of a remote unit. The DAS 1000 in thisexample is an optical fiber-based DAS that is comprised of three (3)main components. One or more radio interface circuits provided in theform of radio interface modules (RIMS) 1004(1)-1004(T) are provided in acentral unit 1006 to receive and process downlink electricalcommunications signals 1008D(1)-1008D(S) prior to optical conversioninto downlink optical communications signals. The downlink electricalcommunications signals 1008D(1)-1008D(S) may be received from a basetransceiver station (BTS) or baseband unit (BBU) as examples. Thedownlink electrical communications signals 1008D(1)-1008D(S) may beanalog signals or digital signals that can be sampled and processed asdigital information. The RIMs 1004(1)-1004(T) provide both downlink anduplink interfaces for signal processing. The notations “1-S” and “1-T”indicate that any number of the referenced component, 1-S and 1-T,respectively, may be provided.

With continuing reference to FIG. 10 , the central unit 1006 isconfigured to accept the plurality of RIMs 1004(1)-1004(T) as modularcomponents that can easily be installed and removed or replaced in achassis. In one embodiment, the central unit 1006 is configured tosupport up to twelve (12) RIMS 1004(1)-1004(12). Each RIM1004(1)-1004(T) can be designed to support a particular type of radiosource or range of radio sources (i.e., frequencies) to provideflexibility in configuring the central unit 1006 and the DAS 1000 tosupport the desired radio sources. For example, one RIM 1004(1)-1004(T)may be configured to support the Personal Communication Services (PCS)radio band. Another RIM 1004(1)-1004(T) may be configured to support the700 MHz radio band. In this example, by inclusion of these RIMS1004(1)-1004(T), the central unit 1006 could be configured to supportand distribute communications signals, including those for thecommunications services and communications bands described above asexamples.

The RIMs 1004(1)-1004(T) may be provided in the central unit 1006 thatsupport any frequencies desired, including, but not limited to, licensedUS FCC and Industry Canada frequencies (824-849 MHz on uplink and869-894 MHz on downlink), US FCC and Industry Canada frequencies(1850-1915 MHz on uplink and 1930-1995 MHz on downlink), US FCC andIndustry Canada frequencies (1710-1755 MHz on uplink and 2110-2155 MHzon downlink), US FCC frequencies (698-716 MHz and 776-787 MHz on uplinkand 728-746 MHz on downlink), EU R & TTE frequencies (880-915 MHz onuplink and 925-960 MHz on downlink), EU R & TTE frequencies (1710-1785MHz on uplink and 1805-1880 MHz on downlink), EU R & TTE frequencies(1920-1980 MHz on uplink and 2110-2170 MHz on downlink), US FCCfrequencies (806-824 MHz on uplink and 851-869 MHz on downlink), US FCCfrequencies (896-901 MHz on uplink and 929-941 MHz on downlink), US FCCfrequencies (793-805 MHz on uplink and 763-775 MHz on downlink), and USFCC frequencies (2495-2690 MHz on uplink and downlink).

With continuing reference to FIG. 10 , the received downlink electricalcommunications signals 1008D(1)-1008D(S) are provided to a plurality ofoptical interfaces provided in the form of optical interface modules(OIMs) 1010(1)-1010(W) in this embodiment to convert the downlinkelectrical communications signals 1008D(1)-1008D(S) into downlinkoptical communications signals 1012D(1)-1012D(S). The notation “1-W”indicates that any number of the referenced component 1-W may beprovided. The OIMs 1010(1)-1010(W) may include one or more opticalinterface components (OICs) that contain electrical-to-optical (E-O)converters 1016(1)-1016(W) to convert the received downlink electricalcommunications signals 1008D(1)-1008D(S) into the downlink opticalcommunications signals 1012D(1)-1012D(S). The OIMs 1010(1)-1010(W)support the radio bands that can be provided by the RIMs1004(1)-1004(T), including the examples previously described above. Thedownlink optical communications signals 1012D(1)-1012D(S) arecommunicated over a downlink optical fiber communications link 1014D toa plurality of remote sub-units (e.g., remote sub-units 504, 904)provided in the form of remote sub-units in this example. One or more ofthe downlink optical communications signals 1012D(1)-1012D(S) can bedistributed to each remote sub-unit. Thus, the distribution of thedownlink optical communications signals 1012D(1)-1012D(S) from thecentral unit 1006 to the remote sub-units is in a point-to-multipointconfiguration in this example.

With continuing reference to FIG. 10 , the remote sub-units includeoptical-to-electrical (O-E) converters 1020(1)-1020(X) configured toconvert the one or more received downlink optical communications signals1012D(1)-1012D(S) back into the downlink electrical communicationssignals 1008D(1)-1008D(S) to be wirelessly radiated through antennas1022(1)-1022(X) in the remote sub-units to user equipment (not shown) inthe reception range of the antennas 1022(1)-1022(X). The notation “1-X”indicates that any number of the referenced component 1-X may beprovided. The OIMs 1010(1)-1010(W) may also include O-E converters1024(1)-1024(W) to convert received uplink optical communicationssignals 1012U(1)-1012U(X) from the remote sub-units into uplinkelectrical communications signals 1026U(1)-1026U(S) as will be describedin more detail below.

With continuing reference to FIG. 10 , the remote sub-units are alsoconfigured to receive uplink electrical communications signals1028U(1)-1028U(X) received by the respective antennas 1022(1)-1022(X)from client devices in wireless communication range of the remotesub-units. The uplink electrical communications signals1028U(1)-1028U(S) may be analog signals or digital signals that can besampled and processed as digital information. The remote sub-unitsinclude E-O converters 1029(1)-1029(X) to convert the received uplinkelectrical communications signals 1028U(1)-1028U(X) into uplink opticalcommunications signals 1012U(1)-1012U(X). The remote sub-unitsdistribute the uplink optical communications signals 1012U(1)-1012U(X)over an uplink optical fiber communications link 1014U to the OIMs1010(1)-1010(W) in the central unit 1006. The O-E converters1024(1)-1024(W) convert the received uplink optical communicationssignals 1012U(1)-1012U(X) into uplink electrical communications signals1030U(1)-1030U(X), which are processed by the RIMs 1004(1)-1004(T) andprovided as the uplink electrical communications signals1030U(1)-1030U(X) to a source transceiver such as a BTS or BBU.

Note that the downlink optical fiber communications link 1014D and theuplink optical fiber communications link 1014U coupled between thecentral unit 1006 and the remote sub-units may be a common optical fibercommunications link, wherein for example, wave division multiplexing(WDM) may be employed to carry the downlink optical communicationssignals 1012D(1)-1012D(S) and the uplink optical communications signals1012U(1)-1012U(X) on the same optical fiber communications link.Alternatively, the downlink optical fiber communications link 1014D andthe uplink optical fiber communications link 1014U coupled between thecentral unit 1006 and the remote sub-units may be single, separateoptical fiber communications links, wherein for example, wave divisionmultiplexing (WDM) may be employed to carry the downlink opticalcommunications signals 1012D(1)-1012D(S) on one common downlink opticalfiber and the uplink optical communications signals 1012U(1)-1012U(X) ona separate, only uplink optical fiber. Alternatively, the downlinkoptical fiber communications link 1014D and the uplink optical fibercommunications link 1014U coupled between the central unit 1006 and theremote sub-units may be separate optical fibers dedicated to andproviding a separate communications link between the central unit 1006and each remote sub-unit.

The DAS 1000 and its PDN 500 or 900 can be provided in an indoorenvironment as illustrated in FIG. 11 . FIG. 11 is a partially schematiccut-away diagram of a building infrastructure 1100 employing the PDN 500of FIG. 5 or the PDN 900 of FIG. 9 . The building infrastructure 1100 inthis embodiment includes a first (ground) floor 1102(1), a second floor1102(2), and an Fth floor 1102(F), where ‘F’ can represent any number offloors. The floors 1102(1)-1102(F) are serviced by the central unit 1006to provide antenna coverage areas 1104 in the building infrastructure1100. The central unit 1006 is communicatively coupled to a signalsource 1106, such as a BTS or BBU, to receive the downlink electricalcommunications signals 1008D(1)-1008D(S). The central unit 1006 iscommunicatively coupled to the remote sub-units to receive uplinkoptical communications signals 1012U(1)-1012U(X) from the remotesub-units as previously described in FIG. 10 . The downlink and uplinkoptical communications signals 1012D(1)-1012D(S), 1012U(1)-1012U(X) aredistributed between the central unit 1006 and the remote sub-units overa riser cable 1108 in this example. The riser cable 1108 may be routedthrough interconnect units (ICUs) 1110(1)-1110(F) dedicated to eachfloor 1102(1)-1102(F) for routing the downlink and uplink opticalcommunications signals 1012D(1)-1012D(S), 1012U(1)-1012U(X) to theremote sub-units. The ICUs 1110(1)-1110(F) may also include respectivepower distribution circuits that include power sources as part of thePDN 500, 900, wherein the power distribution circuits are configured todistribute power remotely to the remote sub-units to provide power foroperating the power-consuming components in the remote sub-units. Forexample, array cables 1112(1)-1112(2F) may be provided and coupledbetween the ICUs 1110(1)-1110(F) that contain both optical fibers toprovide the respective downlink and uplink optical fiber communicationsmedia 1014D(1)-1014D(2F), 1014U(1)-1014U(2F) and power conductors (e.g.,electrical wire) to carry current from the respective power distributioncircuits to the remote sub-units.

FIG. 12 is a schematic diagram of an exemplary mobile telecommunicationsenvironment 1200 that includes an exemplary radio access network (RAN)that includes a mobile network operator (MNO) macrocell employing aradio node, a shared spectrum cell employing a radio node, an exemplarysmall cell RAN employing a multi-operator radio node located within anenterprise environment as DCSs, and that can include one or more PDN,including the PDN 500 of FIG. 5 or the PDN 900 of FIG. 9 . Theenvironment 1200 includes exemplary macrocell RANs 1202(1)-1202(M)(“macrocells 1202(1)-1202(M)”) and an exemplary small cell RAN 1204located within an enterprise environment 1206 and configured to servicemobile communications between a user mobile communications device1208(1)-1208(N) to an MNO 1210. A serving RAN for a user mobilecommunications device 1208(1)-1208(N) is a RAN or cell in the RAN inwhich the user mobile communications devices 1208(1)-1208(N) have anestablished communications session with the exchange of mobilecommunications signals for mobile communications. Thus, a serving RANmay also be referred to herein as a serving cell. For example, the usermobile communications devices 1208(3)-1208(N) in FIG. 12 are beingserviced by the small cell RAN 1204, whereas user mobile communicationsdevices 1208(1) and 1208(2) are being serviced by the macrocell 1202.The macrocell 1202 is an MNO macrocell in this example. However, ashared spectrum RAN 1203 (also referred to as “shared spectrum cell1203”) includes a macrocell in this example and supports communicationson frequencies that are not solely licensed to a particular MNO and thusmay service user mobile communications devices 1208(1)-1208(N)independent of a particular MNO. For example, the shared spectrum cell1203 may be operated by a third party that is not an MNO and wherein theshared spectrum cell 1203 supports Citizen Broadband Radio Service(CBRS). Also, as shown in FIG. 12 , the MNO macrocell 1202, the sharedspectrum cell 1203, and/or the small cell RAN 1204 can interface with ashared spectrum DCS 1201 supporting coordination of distribution ofshared spectrum from multiple service providers to remote sub-units tobe distributed to subscriber devices. The MNO macrocell 1202, the sharedspectrum cell 1203, and the small cell RAN 1204 may be neighboring radioaccess systems to each other, meaning that some or all can be inproximity to each other such that a user mobile communications device1208(1)-1208(N) may be able to be in communications range of two or moreof the MNO macrocell 1202, the shared spectrum cell 1203, and the smallcell RAN 1204 depending on the location of user mobile communicationsdevices 1208(1)-1208(N).

In FIG. 12 , the mobile telecommunications environment 1200 in thisexample is arranged as an LTE (Long Term Evolution) system as describedby the Third Generation Partnership Project (3GPP) as an evolution ofthe GSM/UMTS standards (Global System for Mobile communication/UniversalMobile Telecommunications System). It is emphasized, however, that theaspects described herein may also be applicable to other network typesand protocols. The mobile telecommunications environment 1200 includesthe enterprise environment 1206 in which the small cell RAN 1204 isimplemented. The small cell RAN 1204 includes a plurality of small cellradio nodes 1212(1)-1212(C). Each small cell radio node 1212(1)-1212(C)has a radio coverage area (graphically depicted in the drawings as ahexagonal shape) that is commonly termed a “small cell.” A small cellmay also be referred to as a femtocell or, using terminology defined by3GPP, as a Home Evolved Node B (HeNB). In the description that follows,the term “cell” typically means the combination of a radio node and itsradio coverage area unless otherwise indicated.

In FIG. 12 , the small cell RAN 1204 includes one or more services nodes(represented as a single services node 1214) that manage and control thesmall cell radio nodes 1212(1)-1212(C). In alternative implementations,the management and control functionality may be incorporated into aradio node, distributed among nodes, or implemented remotely (i.e.,using infrastructure external to the small cell RAN 1204). The smallcell radio nodes 1212(1)-1212(C) are coupled to the services node 1214over a direct or local area network (LAN) connection 1216 as an example,typically using secure IPsec tunnels. The small cell radio nodes1212(1)-1212(C) can include multi-operator radio nodes. The servicesnode 1214 aggregates voice and data traffic from the small cell radionodes 1212(1)-1212(C) and provides connectivity over an IPsec tunnel toa security gateway (SeGW) 1218 in a network 1220 (e.g., evolved packetcore (EPC) network in a 4G network, or 5G Core in a 5G network) of theMNO 1210. The network 1220 is typically configured to communicate with apublic switched telephone network (PSTN) 1222 to carry circuit-switchedtraffic, as well as for communicating with an external packet-switchednetwork such as the Internet 1224.

The environment 1200 also generally includes a node (e.g., eNodeB orgNodeB) base station, or “macrocell” 1202. The radio coverage area ofthe macrocell 1202 is typically much larger than that of a small cellwhere the extent of coverage often depends on the base stationconfiguration and surrounding geography. Thus, a given user mobilecommunications device 1208(1)-1208(N) may achieve connectivity to thenetwork 1220 (e.g., EPC network in a 4G network, or 5G Core in a 5Gnetwork) through either a macrocell 1202 or small cell radio node1212(1)-1212(C) in the small cell RAN 1204 in the environment 1200.

FIG. 13 is a schematic diagram illustrating exemplary DCSs 1300 thatsupport 4G and 5G communications services. The DCSs 1300 in FIG. 13 caninclude one or more PDNs, including the PDN 500 in FIG. 5 or the PDN 900of FIG. 9 . The DCSs 1300 support both legacy 4G LTE, 4G/5Gnon-standalone (NSA), and 5G communications systems. As shown in FIG. 13, a centralized services node 1302 is provided that is configured tointerface with a core network to exchange communications data anddistribute the communications data as radio signals to remote sub-units.In this example, the centralized services node 1302 is configured tosupport distributed communications services to a millimeter wave (mmW)radio node 1304. The functions of the centralized services node 1302 canbe virtualized through an x2 interface 1306 to another services node1308. The centralized services node 1302 can also include one or moreinternal radio nodes that are configured to be interfaced with adistribution node 1310 to distribute communications signals for theradio nodes to an open RAN (O-RAN) remote unit 1312 that is configuredto be communicatively coupled through an O-RAN interface 1314.

The centralized services node 1302 can also be interfaced through an x2interface 1316 to a BBU 1318 that can provide a digital signal source tothe centralized services node 1302. The BBU 1318 is configured toprovide a signal source to the centralized services node 1302 to provideradio source signals 1320 to the O-RAN remote unit 1312 as well as to adistributed router unit (DRU) 1322 as part of a digital DAS. The DRU1322 is configured to split and distribute the radio source signals 1320to different types of remote sub-units, including a lower-power remoteunit (LPR) 1324, a radio antenna unit (dRAU) 1326, a mid-power remoteunit (dMRU) 1328, and a high-power remote unit (dHRU) 1330. The BBU 1318is also configured to interface with a third party central unit 1332and/or an analog source 1334 through a radio frequency (RF)/digitalconverter 1336.

FIG. 14 is a schematic diagram representation of additional detailillustrating a computer system 1400 that could be employed in anycomponent or circuit in a PDN, including the PDN 500 or 900 in FIG. 5 or9 . In this regard, the computer system 1400 is adapted to executeinstructions from an exemplary computer-readable medium to perform theseand/or any of the functions or processing described herein. The computersystem 1400 in FIG. 14 may include a set of instructions that may beexecuted to program and configure programmable digital signal processingcircuits in a DCS for supporting scaling of supported communicationsservices. The computer system 1400 may be connected (e.g., networked) toother machines in a LAN, an intranet, an extranet, or the Internet.While only a single device is illustrated, the term “device” shall alsobe taken to include any collection of devices that individually orjointly execute a set (or multiple sets) of instructions to perform anyone or more of the methodologies discussed herein. The computer system1400 may be a circuit or circuits included in an electronic board card,such as, a printed circuit board (PCB), a server, a personal computer, adesktop computer, a laptop computer, a personal digital assistant (PDA),a computing pad, a mobile device, or any other device, and mayrepresent, for example, a server or a user's computer.

The exemplary computer system 1400 in this embodiment includes aprocessing circuit or processor 1402, a main memory 1404 (e.g.,read-only memory (ROM), flash memory, dynamic random access memory(DRAM), such as synchronous DRAM (SDRAM), etc.), and a static memory1406 (e.g., flash memory, static random access memory (SRAM), etc.),which may communicate with each other via a data bus 1408.Alternatively, the processor 1402 may be connected to the main memory1404 and/or static memory 1406 directly or via some other connectivitymeans. The processor 1402 may be a controller, and the main memory 1404or static memory 1406 may be any type of memory.

The processor 1402 represents one or more general-purpose processingdevices, such as a microprocessor, central processing unit, or the like.More particularly, the processor 1402 may be a complex instruction setcomputing (CISC) microprocessor, a reduced instruction set computing(RISC) microprocessor, a very long instruction word (VLIW)microprocessor, a processor implementing other instruction sets, orother processors implementing a combination of instruction sets. Theprocessor 1402 is configured to execute processing logic in instructionsfor performing the operations and steps discussed herein.

The computer system 1400 may further include a network interface device1410. The computer system 1400 also may or may not include an input1412, configured to receive input and selections to be communicated tothe computer system 1400 when executing instructions. The computersystem 1400 also may or may not include an output 1414, including, butnot limited to, a display, a video display unit (e.g., a liquid crystaldisplay (LCD) or a cathode ray tube (CRT)), an alphanumeric input device(e.g., a keyboard), and/or a cursor control device (e.g., a mouse).

The computer system 1400 may or may not include a data storage devicethat includes instructions 1416 stored in a computer-readable medium1418. The instructions 1416 may also reside, completely or at leastpartially, within the main memory 1404 and/or within the processor 1402during execution thereof by the computer system 1400, the main memory1404 and the processor 1402 also constituting computer-readable medium.The instructions 1416 may further be transmitted or received over anetwork 1420 via the network interface device 1410.

While the computer-readable medium 1418 is shown in an exemplaryembodiment to be a single medium, the term “computer-readable medium”should be taken to include a single medium or multiple media (e.g., acentralized or distributed database, and/or associated caches andservers) that store the one or more sets of instructions. The term“computer-readable medium” shall also be taken to include any mediumthat is capable of storing, encoding, or carrying a set of instructionsfor execution by the processing device and that cause the processingdevice to perform any one or more of the methodologies of theembodiments disclosed herein. The term “computer-readable medium” shallaccordingly be taken to include, but not be limited to, solid-statememories, optical medium, and magnetic medium.

The embodiments disclosed herein include various steps. The steps of theembodiments disclosed herein may be performed by hardware components ormay be embodied in machine-executable instructions, which may be used tocause a general-purpose or special-purpose processor programmed with theinstructions to perform the steps. Alternatively, the steps may beperformed by a combination of hardware and software.

The embodiments disclosed herein may be provided as a computer programproduct, or software, that may include a machine-readable medium (orcomputer-readable medium) having stored thereon instructions, which maybe used to program a computer system (or other electronic devices) toperform a process according to the embodiments disclosed herein. Amachine-readable medium includes any mechanism for storing ortransmitting information in a form readable by a machine (e.g., acomputer). For example, a machine-readable medium includes amachine-readable storage medium (e.g., read only memory (“ROM”), randomaccess memory (“RAM”), magnetic disk storage medium, optical storagemedium, flash memory devices, etc.), a machine-readable transmissionmedium (electrical, optical, acoustical or other form of propagatedsignals (e.g., carrier waves, infrared signals, digital signals, etc.)),etc.

Unless specifically stated otherwise as apparent from the previousdiscussion, it is appreciated that throughout the description,discussions utilizing terms such as “processing,” “computing,”“determining,” “displaying,” or the like, refer to the action andprocesses of a computer system, or similar electronic computing device,that manipulates and transforms data represented as physical(electronic) quantities within the computer system's registers andmemories into other data similarly represented as physical quantitieswithin the computer system memories or registers or other suchinformation storage, transmission, or display devices.

The algorithms and displays presented herein are not inherently relatedto any particular computer or other apparatus. Various systems may beused with programs in accordance with the teachings herein, or it mayprove convenient to construct more specialized apparatuses to performthe required method steps. The required structure for a variety of thesesystems will appear from the description above. In addition, theembodiments described herein are not described with reference to anyparticular programming language. It will be appreciated that a varietyof programming languages may be used to implement the teachings of theembodiments as described herein.

Those of skill in the art would further appreciate that the variousillustrative logical blocks, modules, circuits, and algorithms describedin connection with the embodiments disclosed herein may be implementedas electronic hardware, instructions stored in memory or in anothercomputer-readable medium and executed by a processor or other processingdevice, or combinations of both. The components of the distributedantenna systems described herein may be employed in any circuit,hardware component, integrated circuit (IC), or IC chip, as examples.Memory disclosed herein may be any type and size of memory and may beconfigured to store any type of information desired. To clearlyillustrate this interchangeability, various illustrative components,blocks, modules, circuits, and steps have been described above generallyin terms of their functionality. How such functionality is implementeddepends upon the particular application, design choices, and/or designconstraints imposed on the overall system. Skilled artisans mayimplement the described functionality in varying ways for eachparticular application, but such implementation decisions should not beinterpreted as causing a departure from the scope of the presentembodiments.

The various illustrative logical blocks, modules, and circuits describedin connection with the embodiments disclosed herein may be implementedor performed with a processor, a Digital Signal Processor (DSP), anApplication Specific Integrated Circuit (ASIC), a Field ProgrammableGate Array (FPGA) or other programmable logic device, discrete gate ortransistor logic, discrete hardware components, or any combinationthereof designed to perform the functions described herein. A controllermay be a processor. A processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

The embodiments disclosed herein may be embodied in hardware and ininstructions that are stored in hardware, and may reside, for example,in Random Access Memory (RAM), flash memory, Read Only Memory (ROM),Electrically Programmable ROM (EPROM), Electrically ErasableProgrammable ROM (EEPROM), registers, a hard disk, a removable disk, aCD-ROM, or any other form of computer-readable medium known in the art.An exemplary storage medium is coupled to the processor such that theprocessor can read information from, and write information to, thestorage medium. In the alternative, the storage medium may be integralto the processor. The processor and the storage medium may reside in anASIC. The ASIC may reside in a remote station. In the alternative, theprocessor and the storage medium may reside as discrete components in aremote station, base station, or server.

It is also noted that the operational steps described in any of theexemplary embodiments herein are described to provide examples anddiscussion. The operations described may be performed in numerousdifferent sequences other than the illustrated sequences. Furthermore,operations described in a single operational step may actually beperformed in a number of different steps. Additionally, one or moreoperational steps discussed in the exemplary embodiments may becombined. It is to be understood that the operational steps illustratedin the flow chart diagrams may be subject to numerous differentmodifications as will be readily apparent to one of skill in the art.Those of skill in the art would also understand that information may berepresented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,bits, symbols, and chips that may be referenced throughout the abovedescription may be represented by voltages, currents, electromagneticwaves, magnetic fields or particles, optical fields or particles, or anycombination thereof.

Further, as used herein, it is intended that terms “fiber optic cables”and/or “optical fibers” include all types of single mode and multi-modelight waveguides, including one or more optical fibers that may beupcoated, colored, buffered, ribbonized and/or have other organizing orprotective structure in a cable such as one or more tubes, strengthmembers, jackets or the like. The optical fibers disclosed herein can besingle mode or multi-mode optical fibers. Likewise, other types ofsuitable optical fibers include bend-insensitive optical fibers, or anyother expedient of a medium for transmitting light signals. An exampleof a bend-insensitive, or bend resistant, optical fiber is ClearCurve®Multimode fiber commercially available from Corning Incorporated.Suitable fibers of this type are disclosed, for example, in U.S. PatentApplication Publication Nos. 2008/0166094 and 2009/0169163, thedisclosures of which are incorporated herein by reference in theirentireties.

Many modifications and other embodiments of the embodiments set forthherein will come to mind to one skilled in the art to which theembodiments pertain having the benefit of the teachings presented in theforegoing descriptions and the associated drawings. For example, theantenna arrangements may include any type of antenna desired, includingbut not limited to dipole, monopole, and slot antennas. The distributedantenna systems that employ the antenna arrangements disclosed hereincould include any type or number of communications mediums, includingbut not limited to electrical conductors, optical fiber, and air (i.e.,wireless transmission). The distributed antenna systems may distributeand the antenna arrangements disclosed herein may be configured totransmit and receive any type of communications signals, including butnot limited to RF communications signals and digital data communicationssignals, examples of which are described in U.S. patent application Ser.No. 12/892,424 entitled “Providing Digital Data Services in OpticalFiber-based Distributed Radio Frequency (RF) Communications Systems, AndRelated Components and Methods,” published as U.S. Patent ApplicationPublication No. 2011/0268446, incorporated herein by reference in itsentirety. Multiplexing, such as WDM and/or FDM, may be employed in anyof the distributed antenna systems described herein, such as accordingto the examples provided in U.S. patent application Ser. No. 12/892,424.

Therefore, it is to be understood that the description and claims arenot to be limited to the specific embodiments disclosed and thatmodifications and other embodiments are intended to be included withinthe scope of the appended claims. It is intended that the embodimentscover the modifications and variations of the embodiments provided theycome within the scope of the appended claims and their equivalents.Although specific terms are employed herein, they are used in a genericand descriptive sense only and not for purposes of limitation.

What is claimed is:
 1. A power distribution network (PDN) comprising: apower source comprising: a power input configured to receive power; apower output port; a first conductor coupling the power input to thepower output port; a first current sensor associated with the firstconductor and configured to measure current on the first conductor; afirst switch associated with the first conductor; and a control circuitconfigured to: receive information from the first current sensor; andopen the first switch responsive to the information indicating anovercurrent situation on the first conductor; a power conductor paircoupled to the power output port; and a remote sub-unit, comprising: aremote sub-unit power input port coupled to the power conductor pair; afirst diode coupled to the remote sub-unit power input port and a firstone of the power conductor pair; and a second diode coupled to theremote sub-unit power input port and a second one of the power conductorpair, wherein each remote sub-unit comprises at least one antenna.
 2. Adistributed communication system (DCS), comprising: a power distributionnetwork (PDN), comprising: a power source comprising: a power inputconfigured to receive power; a power output port; a first conductorcoupling the power input to the power output port; a first currentsensor associated with the first conductor and configured to measurecurrent on the first conductor; a first switch associated with the firstconductor; and a control circuit configured to: receive information fromthe first current sensor; and open the first switch responsive to theinformation indicating an overcurrent situation on the first conductor;a power conductor pair coupled to the power output port; and a pluralityof remote sub-units, each remote sub-unit comprising: a remote sub-unitpower input port coupled to the power conductor pair; a first diodecoupled to the remote sub-unit power input port and a first one of thepower conductor pair; and a second diode coupled to the remote sub-unitpower input port and a second one of the power conductor pair; and acentral unit configured to: distribute received one or more downlinkcommunications signals over one or more downlink communications links toone or more remote sub-units; and distribute received one or more uplinkcommunications signals from the one or more remote sub-units from one ormore uplink communications links to one or more source communicationsoutputs; each remote sub-unit among the plurality of remote sub-unitsconfigured to: distribute the received one or more downlinkcommunications signals received from the one or more downlinkcommunications links to one or more client devices; and distribute thereceived one or more uplink communications signals from the one or moreclient devices to the one or more uplink communications links.
 3. TheDCS of claim 2, wherein the central unit is configured to: distributeeach of the received one or more downlink communications signals over adistribution communications output among a plurality of distributioncommunications outputs to a downlink communications link among the oneor more downlink communications links; and distribute each of thereceived one or more uplink communications signals from an uplinkcommunications link among the one or more uplink communications links ona distribution communications input among a plurality of distributioncommunications inputs to the one or more source communications outputs.4. The DCS of claim 2, comprising a distributed antenna system (DAS). 5.The DCS of claim 2, wherein: the one or more downlink communicationslinks comprise one or more optical downlink communications links; theone or more uplink communications links comprise one or more opticaluplink communications links; the central unit further comprises: one ormore electrical-to-optical (E-O) converters configured to convertreceived one or more electrical downlink communications signals into oneor more optical downlink communications signals; and one or moreoptical-to-electrical (O-E) converters configured to convert receivedone or more optical uplink communications signals into one or moreelectrical uplink communications signals; the central unit is furtherconfigured to: distribute the one or more optical downlinkcommunications signals from the one or more E-O converters over aplurality of optical distribution communications outputs to the one ormore optical downlink communications links; and distribute the receivedone or more optical uplink communications signals from the one or moreoptical uplink communications links on a plurality of opticaldistribution communications inputs to the one or more O-E converters;each remote unit among the plurality of remote sub-units furthercomprises: one or more O-E converters configured to convert the receivedone or more optical downlink communications signals into one or moreelectrical downlink communications signals; one or more E-O convertersconfigured to convert the received one or more electrical uplinkcommunications signals into one or more optical uplink communicationssignals; and each remote unit among the plurality of remote sub-units isconfigured to: distribute the one or more electrical downlinkcommunications signals from the one or more O-E converters to the one ormore client devices; and distribute the one or more optical uplinkcommunications signals from the one or more E-O converters to the one ormore optical downlink communications links.
 6. The DCS of claim 2,wherein: the one or more downlink communications links comprise one ormore optical downlink communications links; and the one or more uplinkcommunications links comprise one or more optical uplink communicationslinks.
 7. The DCS of claim 6, comprising a distributed antenna system(DAS).
 8. The DCS of claim 6, wherein the central unit furthercomprises: one or more electrical-to-optical (E-O) converters configuredto convert received one or more electrical downlink communicationssignals into one or more optical downlink communications signals; andone or more optical-to-electrical (O-E) converters configured to convertreceived one or more optical uplink communications signals into one ormore electrical uplink communications signals.
 9. The DCS of claim 8,comprising a distributed antenna system (DAS).
 10. The DCS of claim 8,wherein the central unit is further configured to: distribute the one ormore optical downlink communications signals from the one or more E-Oconverters over a plurality of optical distribution communicationsoutputs to the one or more optical downlink communications links; anddistribute the received one or more optical uplink communicationssignals from the one or more optical uplink communications links on aplurality of optical distribution communications inputs to the one ormore O-E converters.
 11. The DCS of claim 10, wherein each remote unitamong the plurality of remote sub-units further comprises: one or moreO-E converters configured to convert the received one or more opticaldownlink communications signals into one or more electrical downlinkcommunications signals; one or more E-O converters configured to convertthe received one or more electrical uplink communications signals intoone or more optical uplink communications signals.
 12. The DCS of claim11, wherein each remote unit among the plurality of remote sub-units isconfigured to: distribute the one or more electrical downlinkcommunications signals from the one or more O-E converters to the one ormore client devices; and distribute the one or more optical uplinkcommunications signals from the one or more E-O converters to the one ormore optical downlink communications links.
 13. The DCS of claim 2,comprising a distributed antenna system (DAS).
 14. The DCS of claim 6,wherein each remote unit among the plurality of remote sub-unitscomprises at least one antenna.
 15. The DCS of claim 10, wherein eachremote unit among the plurality of remote sub-units comprises at leastone antenna.